Modern electronic components utilize numerous integrated circuits. Often, these integrated circuits must be electrically connected to each other or to other electronic components. One method for connecting integrated circuits to electronic components utilizes a ball grid array electronic package. With a ball grid array electronic package, various input and output ports of an integrated circuit are typically connected via wire bonds to contact pads on the ball grid array electronic package. Solder formed on the contact pads of the ball grid array electronic package are used to complete the connection to another electronic component, such as a printed circuit board. Integrated circuits are also connected to electronic components through a flip-chip electronic package design. The flip-chip electronic package is similar to the ball grid array electronic package in that solder is used to make a connection with other electronic components, such as a printed circuit board. However, solder in a flip-chip design is attached directly to the input and output ports on the face of the integrated circuit. Flip-chip packages do not require wire bonds. One important step in the above described methods for interconnecting electronic components is the formation of solder on the ball grid array package or flip-chip electronic package.
Several conventional methods exist for forming solder on a ball grid array or flip-chip electronic packages. Flip-chip solder bumps may be fabricated on the integrated circuit by evaporation or plating. Another method for attaching solder to a ball grid array electronic package comprises the use of a vacuum chuck to transfer preformed solder balls to the contact pads on the ball grid array electronic package. This method suffers several disadvantages. For example, the minimum distance between solder balls that this method allows may be unacceptable for some electronic packages. Additionally, this conventional method may require two vacuum chucks because while one vacuum chuck is transferring solder balls to the ball grid array electronic package, the other is being filled. The use of one or more vacuum chucks increases the expense associated with this method for forming solder balls on an electronic package.
Another conventional method for forming solder on a ball grid array or flip-chip electronic package utilizes a stencil placed on top of the package. In a typical application, solder paste is applied on top of the stencil and then a squeegee is moved across the top of the stencil forcing the solder paste down through the holes until contact is made directly with the contact pads of the ball grid array or flip-chip electronic package. This method also suffers several disadvantages. For example, the ball grid array or flip-chip electronic packages may be exposed to the harshness of the chemical process associated with such a method. In addition, forcing solder paste through a stencil onto an electronic package require forces that may damage the electronic package. Furthermore, the use of such a method may also result in paste in undesired locations that must be cleaned up. These problems are further compounded in standard silkscreen printing approaches where multiple applications of solder layers are often necessary to provide adequate material.